The 34-year-old, who has spent the last four years with the Bluebirds, recently returned to action after a 15-month lay-off, only to suffer a recurrence of the problem.
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The former Aston Villa star said: "There comes a time when you have to call a halt.
"Whatever the temptation to go on, and to try again, you can't ignore what your body is telling you. I've had a good career - it's been great. I feel it's better to be grateful for that rather than think about my regrets about not carrying on as a player.
"Facing the lads and telling them I was finishing was one of the hardest things I've done. I welled up a little bit, but that's to be expected.
"There's a feeling of relief as well but it was very hard to make that decision. It had to come at some stage. I wanted to be the one to make the decision and it's come earlier for me than I'd have liked, but that's the way it goes."
Source: DSG
